Really enjoying reading this series - thanks for putting this together! I do however have a couple of queries about the points above that you label as "concrete evidence":Jeremy noticed that I had done something sneaky. Well, perhaps not so sneaky, he noticed it. And then again, I think sneaky implies the intent to deceive, and that was not my intent. In fact, I think it was just laziness in my writing (and thinking), which is one reason I am trying to pick up my blogging again. But, Jeremy questioned my use of the term "concrete evidence" to refer to the dating of the four canonical gospels to the first century, and he was correct to do so. That would only be "concrete evidence" or "hard data" if we had, say, a dated manuscript, or a datable inscription, or perhaps a datable reference to the gospels that was in the first century. We have none of those. Instead, what we have is a scholarly consensus that the four canonical gospels should be dated in the first century (or, early second century at the latest) and I agree with the substance of the dates that Jeremy gave above.
1) Can we firmly date all four gospels to the first century? What is the evidence for this? The consensus dates are something like 70 AD for Mark, 75 for Matthew, 85 for Luke and 95 for John. But as with the attribution of names that you highlight here, this consensus is based on quite flimsy evidence, and there is actually a high margin for error in all of these dates. This cuts both ways - the actual dates could be either earlier or later - but my understanding is that for John at least (and more controversially also for Luke and possibly even Matthew and Mark) the date could be some time in the second century. And in the case of John, we may have some parts from the first century, and some from the second.
So, I was mistaken in using this scholarly consensus as "concrete evidence." So, what is a scholarly consensus and how should one be used in argumentation?
Well, in short, a scholarly consensus is when the vast majority of scholars in a given field, with the necessary training in that field, have determined, based upon the concrete evidence, that certain conclusions follow the evidence. It is important to note that scholarly consensuses are conclusions based on evidence and are not themselves evidence. This is true in all fields. One could list many examples: the safety of vaccinations, human caused climate change, evolution through natural selection, etc.
Now, some important things to point out. First, scholarly consensuses are not easy to come by. In general, scholars love to argue and debate. They love to one up their colleagues. Moreover, there is probably no quicker way to gain scholarly respect and notoriety than to successfully overturn a scholarly consensus. For example, if I could convince everyone, or nearly everyone in my field, that Q did not exist, then I would overturn a long held scholarly consensus in my field and would gain tremendous respect and notoriety (Oh, wait, someone may be doing this already, but unfortunately it was not me, but Mark Goodacre). So, when scholars nearly all agree the the evidence leads to certain conclusions, those conclusions ought to be taken very seriously. It is not that they cannot be questioned, or even overturned, but that is a hard fought battle.
Now, I do think scholarly consensuses are useful for pursuing an argument, and next to "hard data" they are often the best that scholars can do given the scarcity of evidence in certain cases (like ancient history). In that sense, I would stand by what I wrote in Part V, that the four canonical gospels can be firmly dated to the first century. But, as Jeremy pointed out, this is a scholarly consensus, a conclusion reached by scholars based on the evidence, and is not itself evidence, and I was mistaken in my language in so calling it "concrete evidence."
In fact, the whole gospel authorship series began by questioning an assumption I had made that a scholarly consensus (that the gospel titles were added later and that the gospels are anonymous), a conclusion reached based on the evidence, was in fact evidence in the form of gospel manuscripts without titles. Once again, there are no gospel manuscripts without titles.
So, bully to Jeremy for holding my feet to the fire and forcing me to be more precise in my language.